lnterdiffusion of Potassium and Sodium Ions in Pyrex Glass

Abstract

Diffusion profiles in Pyrex glass after exchange in molten potassium nitrate were obtained by secondary ion mass spectrometry and the chemical etching-flame photometric method over the temperature range 350.450°C (Figs.1, 3, and 4). The former method was applicable to the diffusion in the narrow region within 1, u of the surface. Secondary ion intensity ratios, I (39K+) r(28si+) and /(28Na+)//(28Si+), were proportional to atomic concentrations of potassium and sodium ions in Pyrex glass, respectively (Fig.2). The distortion of the profiles due to ion etching was negligible (Fig.3). The interdiffusion coefficients, which depended on potassium concentration (Fig.5), were described by an Arrhenius' equation D=8.2 X 10-4 exp (-26000/R T) cm². s-1 at about 2 atomic% K, where R is the gas constant in calole-Iegreci and T is the absolute temperature. The results were in good agreement with those estimated from Garfinkel's data (Fig.6).